1. Field of the Invention
The present invention relates to a corrugated plate formed into corrugate shape (wave shape) which is efficiently applied to a cooling fin formed into a corrugated shape in a heat exchanger.
2. Description of Related Art
In general, to modify a heat exchanging ability of a heat exchanger, instead of changing a core width size of a heat exchanger (a size of an air flowing direction), mainly, changing a size of a direction perpendicular to the air flowing direction and the number of tubes is used.
Accordingly, as an outer fin located between the adjacent tubes is arranged in such a manner that a ridge direction of its bent ridge portion is parallel to the air flow direction, the ridge direction size of the outer fin is substantially equal to the core width size. Further, a spreading direction size of the fin is changing in accordance with a length direction size of the tube.
So, the outer fin is, in general, manufactured by feeding an aluminum thin plate, which is a fin material, into a gear type roller forming machine to obtain a corrugate shaped fin material such that the feeding direction is parallel to the spreading direction of the fin, and after that, by cutting the fin material in such a manner that its length is a predetermined value (i.e., the number of the bent ridge is to be a predetermined number).
Heat exchangers have an aluminum inner fin (whose thickness is about 0.1 mm) inside a tube of an inter-cooler or the like for improving heat exchanging ability.
This inner fin is arranged inside the tube in such a manner that a direction of a fluid flowing inside the tube (i.e., a length direction of the tube) is parallel to a bent ridge direction of the inner fin, so, the bent ridge direction of the inner fin is parallel to the length direction of the tube. Accordingly, among an inner fin outer shape size, especially, the bent ridge direction size of the inner fin fluctuates in accordance with a changing of the length direction size of the tube.
The manufacturing method in which the fin material feeding direction is parallel to the fin spreading direction cannot flexibly be applied to, e.g., forming an inner fin in which the bent ridge direction size fluctuates in accordance with the tube length direction size.
Inventors tried to form the bent ridge in such a manner that the bent ridge direction of the fin is parallel to the fin material feeding direction, and, after that, to cut the fin such that its bent ridge direction size is a predetermined value.
However, this method, as shown in FIG. 7, suffers from a difficulty in that the inner fin is warped from substantially the center of a plurality of bent ridges 221.